Many agents have been found which will either block or stimulate cell division. However, generally speaking, these agents will not both block and/or stimulate cell division. Most of the known blocking agents are of a chemical nature quite foreign to the natural metabolic regime of the cell and often induce highly abnormal metabolic conditions leading to cell death or permanent aberrancies of the cell. These types of agents are also generally nonspecific and block division indiscriminately in all cell types. The blockage usually occurs through highly abnormal mechanisms and at abnormal places in the cell's metabolic cycle. The few known mitotic stimulatory agents are generally highly specific in the cell types which they activate, and thus are quite restricted in their usefulness.